imx: Fix missing inclusion of cdefs.h

This was found by compiling with -fno-common:

./build/picopi/release/bl2/imx_snvs.o:(.bss.__packed+0x0): multiple definition of `__packed';
./build/picopi/release/bl2/imx_caam.o:(.bss.__packed+0x0): first defined here

__packed was intended to be the attribute macro from cdefs.h, not an
object of the structure type.
Signed-off-by: Samuel Holland <samuel@sholland.org>
Change-Id: Id02fac3f098be2d71c35c6b4a18012515532f32a

plat/imx/common/include/imx_caam.h

 /*
- * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2018-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -7,6 +7,7 @@
 #ifndef IMX_CAAM_H
 #define IMX_CAAM_H
 
+#include <cdefs.h>
 #include <stdint.h>
 #include <arch.h>
 #include <imx_regs.h>

plat/imx/common/include/imx_snvs.h

 /*
- * Copyright (C) 2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (C) 2018-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 #ifndef IMX_SNVS_H
 #define IMX_SNVS_H
 
+#include <cdefs.h>
 #include <stdint.h>
 
 #include <arch.h>